Things could definately work out as a relationship if you both want it, don't see why they couldn't just because of the circumstances in which you met - although you don't say if they have also said they have these feelings for you too, so take your time don't rush just like you wouldn't in the 'real world'. Be careful that they aren't actually married, girlfriend etc... I do know a few girls not to make you paranoid, that have 'fallen' for clients given them free dates etc, slept with them then either discovered they were seeing many other girls or were already taken. Don't rush into anything. Good Luck!